Actuator motor device for hydraulic brakes



May 12, 19 3 c. R. MYERS ETAL 2,637,976

ACTUATOR MOTOR DEVICE FOR HYDRAULIC BRAKES Filed Aug. 7, 1951 '3Sheets-Sheet l y 1953 c. R. MYERS ET AL 37, 76

ACTUATOR MOTOR DEVICE FOR HYDRAULIC BRAKES Filed Aug. 7, 1951 3Sheets-Sheet 2 FI G. 2.

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y 1953 c. R. MYERS ETAL 37,976

ACTUATOR MOTOR DEVICE FOR HYDRAULIC BRAKES Filed Aug. 7, 1951 3Sheets-Sheet 35 a?! V F N TORS.

Patented May 12, 1953 ACTUATOR MOTOR DEVICE ros HYDRAULIC BRAKES ClaudeR. Myers, Galicn, Lester Dasse, St.

Joseph,

and John Bassett,- Benton Harbor,

Mich, assignors, by mesne assignments, to Lambert Brake Corporation, St.Joseph, Mich, a corporation of Michigan Application August 7, 1951,Serial No. 240,642

16 Claims. 1

The present invention relates to a fluid pressure responsive actuatordevice for use in hydraulic brake systems or the like, wherein apressure fluid is forced from the main or master cylinder to one or moreactuator cylinders, each preferably having a pair of opposed pistonsreciprocally mounted therein and operatively connected to frictionmembers for controlling the application and release of the brakes.

More particularly, the invention concerns means for facilitating thebleeding of air from the hydraulic system in such a manner as toefiectively wash any minute air pockets or bubbles out of each actuatorcylinder.

When air finds access into a hydraulicsystem in which the pressure fluidis utilized to transmit thrust, the operativeness of the system isseriously impaired due to the compressibility of the air. This isespecially true in hydraulic brake systems wherein the air pockets arecompressed by the fluid pressure, and require a substantial increase inthe pedal movement of the conventional brake system, resulting in whatis sometimes referred to as a spongy pedal, and may even require pumpingbefore the brake can be effectively applied.

Another disadvantage of air in a hydraulic brake system, particularly inmotor vehicle installations, is the uneven braking action of the brakeon dilierent wheels caused by air pockets 1 hydraulic fluid, and thenbleed oil the air from these high points.

It is the primary object of the present invention to provide means foreffectively bleeding.

hydraulic brake systems including the actuator cylinders, therebyinsuring that all oi the air therein is removed from the system.

Another object is to provide an improved wheel or actuator cylinder formotor vehicle hydraulic Zil brake systems which attains the foregoingobjectives by the utilization of the means .for sealing the pistons andpiston chambers against loss of hydraulic fluid, this being accomplishedby providing an annular expandable sealing ring within the respectivepiston chambers and a spring-pressed expander ring engaged with saidsealing ring, the expander ringhaving passages .or grooves through whichthe fluid must flow when the actuator is being bled, whereby the fluidis caused tofollow a tortuous path .swirlingfrom one side of the pistonchambers to the other to effectively flush out any and all air bubblesor pockets within the piston chambers.

Other objects and advantages of the invention will be hereinafterdescribed, and the novel features thereof defined in the appendedclaims.

In the accompanying drawings:

Figure 1 is a view in elevation of a disc brake embodying a pair ofactuator cylinders made in accordance with this invention;

Figure 2 is an enlarged view partly in elevation and partly in verticalsection of one of the actuator cylinders of this invention also showingportions of the disc brake assembly which are operated and controlled bythe actuator cylinder;

Figure 3 is a view in vertical section, as taken on the line 3--3 of l-igure 2, with certain of the parts shown in elevation;

ire 4: view in horizontal section, as taken on the line iii of Figure 2;

Figure 5 is a plan view or one of the fluicldirecting expander ringswhich is adapted to encircle the pistons and cause the fluid within thepiston chambers to travel in a tortuous path when the actuator is beingbled;

Figure 6 is a view in vertical section, as taken on the line t6 ofFigure Figure '7 is a transverse sectional view of an annular sealingmember which is utilized to seal each piston in its piston chamber inthe actuator cylinder; and

Figure 8 is a fragmentary View in vertical sec tion of a modified formof actuator cylinder and piston made in accordance with the presentinvention.

Like reference characters designate corresponding parts in the severalfigures of the drawings.

Referring first to Figure l of thedrawings forming a part of the presentapplication, there is shown a disc brake assembly to which the actuatorcylinder of this invention is particularly adaptable, this disc brakebeing the subject of copending application Serial No. 238.283, filedJuly 24, 1951, now Patent No. 2,595,860, dated May 6, 1952.

As more particularly described in that application, the brake includes ahousing, generally designated I, which is preferably made in two partsthat are adapted to be bolted or otherwise fastened together by suitablefastening means (not shown) which extend through spaced openings 2 whichare provided about the periphery of the housing sections, the outboardsection of the housing being omitted to show the interior of the brakeconstruction. The outboard section of the housing is adapted to beconnected by bolts or other suitable fastening means to the usualradially extended flange of a wheel mounting hub (not shown), in thecase of an automobile wheel, so that the entire brake housing or casingI will rotate with the wheel or other rotatable part to be braked, ineither a forward or rearward direction according to the direction ofmovement of the vehicle or other rotary part, as the case may be.

At the inboard side of the brake housing I, there is provided arelatively fixed or stationary backing or adapter plate generallydesignated 3, which forms a closure for the inboard side of the housing.This backing plate 3 is suitably fastened, as by means of bolts 4, to aflange or other part of the usual axle on the vehicle, said axle beingdesignated 5, and in the illustrated embodiment comprising a frontwheel-mounting spindle of a motor vehicle.

Rigidly mounted on and fixed to the backing plate 3 is a pair ofhydraulic actuator or Wheel cylinders generally designated I and 8,respectively, these cylinders being located in diametrically spacedrelation to each other. Hydraulic lines 9, I0 branching from a fittingII which is rigidly supported on the backing plate 3, are respectivelyconnected to the wheel cylinders 'I, 8 for supplying hydraulic fluidunder pressure to these cylinders, this hydraulic fluid being forcedthrough these lines 9, II] by means of a conventional master cylinder(not shown) of the hydraulic brake system of the motor vehicle. Thefitting II, as Well as the branch lines 9, I0, are preferably located onthe outside of the brake assembly at the inboard side thereof, in orderto be connected to the actuator cylinders I, 8 of this invention, bothof which have a cylindrical boss I2 which is adapted to be extendedthrough the backing plate 3 so as to project inwardly beyond the inboardface of this plate, as best seen in Figure 3. The actuators I, 8 arebolted to the backing plate 3, as by means of bolts I3 extend- 4 ingthrough the backing plate and into the cylinder castings of theactuators.

Disposed within the rotary brake housing I and surrounding the actuatorcylinders I, 8, there is provided a double-disc unit generallydesignated I4, said unit including two discs of annular form which arearranged back-to-back, with a series of balls or camming members I5disposed therebetween, said balls being seated in ramped seats formed inthe opposing faces of the respective discs, and being normally held inthese seats by a plurality of springs I6 yieldably connecting the twodiscs together. This arrangement allows the discs to move relative toeach other in both a rotative direction and an axial direction.Accordingly, if a limited. rotative movement is imparted to one of thediscs of the double-disc unit I4, while the other disc of this unit isheld relatively stationary, the discs will spread apart in an axialdirection, responsive to the camming action of the balls I5. As a resultof this spreading of the double-disc unit I4, the discs willfrictionally engage the rotary housing I which is extended on oppositesides of the double-disc unit I4 so as to provide opposed axially spacedbraking surfaces against which the double-disc unit will exert apowerful braking action, each disc of the double-disc unit preferablybeing provided with a series of friction lining segments I! on thehousing-engaging faces of the respective discs. Preferably, thedouble-disc assembly I4 includes automatic adjuster means IT forprogressively compensating for wear of the friction lining segments I'Ithroughout the life of these linings.

In order to actuate the discs of the double-disc assembly I4 to producethe braking action in the manner just described, one of the two discs isprovided with a pair of diametrically spaced lugs I8, in each of whichis rockably seated a rocker or toggle pin I9, the opposite end of eachrocker pin being in turn universally seated in the outer end of one ofthe pistons of the respective wheel cylinders 1, 8, which will behereinafter described in detail. The other disc of the double-disc unitI4 is also provided with a pair of diametrically spaced lugs 20, in eachof which is rockably seated another rocker pin 2|, these pins in turnbeing universally seated in the other piston of the correspondingactuator cylinders I, 8.

Preferably, there is a slight clearance between the wheel cylinders I, 8and the inner peripheries of the discs of the double-disc unit I4 sothat the discs will not actually contact the wheel cylinders in normaluse of the brake, but generally speaking, the wheel cylinders I, 8 areadapted to support the double-disc unit I4 on the rocker pins I9, 2|with the double-disc unit concentrically located and piloted by butfreely floating about the actuator cylinders I, 8.

In energizing or operating the brake shown in Figure l, hydraulic fluidis forced into the wheel cylinders I, 8, between opposed pistons 22, 23in each cylinder, thereby forcing the pistons apart, with consequenttransmission of a rotative thrust against the two discs of thedouble-disc unit I4, and tending to rotate the respective discs inopposite directions, which in turn tends to cause the discs to moveapart in an axial direction, relative to each other, responsive to thecamming action of the balls I5 therebetween. As the double-disc unitengages the rotary housing I which is connected to a wheel or otherrotary part to be braked, the frictional drag imparted by the rotaryhousing to the double-disc unit tends to clock the double-disc unit in adirectioncorresponding to the direction of rotation'ofthe housing I,thereby forcing one of the pistons of-"each actuator "i, 8 inwardly ofthe cylinders until a portion of these pistons engages a portion of theactuator cylinder, thereby stopping further clocking movement of thedouble one unit, and anchoring one of the discsof said u it againstrotation, while leaving the other disc of said double-disc unit free torotate slightly relative to the anchored disc in response to continuedpressure in the actuator cylinders and the energizing force provided bythe camrning action of the relatively rotatable disc.

The fluid pressure-responsive actuators l, 8, of this invention, whichare primarily intended and constructed for use with brakes of thejust-described type, but are not limited to such use, will now describedin. detail.

l-teferring more particularly to Figures 2, 3 and l, each wheel cylindercomprises a body ml which is preferably a one-piece casting having acentrally located partition 25 and opposed piston chambers 28, 27disposed within the body 2d on opposite sides of the partition 25 andextending axially therefrom in opposite directions. One longitudinalside of the body it is laterally extended to provide a mounting portion28 which is adapted to butt up against the backing plate 3 of a brakeconstruction, with the aforementioned cylindrical boss i2 projectingthrough said backing plate, the bolts 83 also extending" through saidbacking plate and into the portion 28 for rigidly mounting the wheelcylinder on the backing plate 3.

The portion of the cylindrical boss l2 which projects inwardly past theinboard side or the backing plate 3 has angularly disposed faces 29diverging toward the backing plate 3. The body is provided with aninlet-outlet opening 36' can tending at a right angle from one of theinclined faces through the cylindrical boss 22 and into the pistonchamber 2'? adjacent to the central partition this inlet-outlet openingbeing enlarged and screw-threaded, as at 3|, at its outer end forconnection with one of the branch lines 5. ill. The portion 28 of thebody 2 is also provided wi h a bleed opening extending into the rnberthe outer end of this opening a bleeder valve (not shown). The back- 3is provided with an opening 3% there- 11 axial alignment with the bleedpasto accommodate the aforementioned breeder valve. Tre cent a].partition 25 is provided with. a relatively small fluid passage 35thcrethrough, whereby fluid under pressure may pass into the pistonchamber 28 from the piston chamber El, and vice versa, thus passage 35not only establishing communication between the piston chambers and 27,but also serving to restrict the fluid flow thercthrough and thus dampor cushion the inward movements of the pistons 22:3 during clocking ofthe double-disc unit it in either direction, thereby eliminating noisethat oi erwise would result from metalto-inetal Contact of the pistonsag inst the partition 25 in e horing one of the discs against rotationduring the braking action.

The pistons 23 in the embodiment shown in Figures 2-, 3 and l, eachinclude a reduced shank 3E3, this shank 35 being adapted to abut againstthe inner partition 25 for limiting inward movement of the pistonswithin the piston chambers it, '27. The outer end of each piston ed andscrew-threaded, as at 33, for

22, 23 is provided with asubstantially conical recess 3'! in which therocker ortoggle pins i9, 2! are universally seated. The outer ends ofthe rocker pins is, ii are each provided with a substantiallyhemispherical head 36 which i'oclrably seats in the lugs i5, 26 on thediscs of the doubledisc unit i i. The rocker pins are each provided withan annular recess 3-8 for receiving an annular shoulder 39' defining acentral opening in a resilient dust-cap to, these dust-caps lil alsohaving a shoulder ll adapted to be snapped into a peripheral groove orrecess ll ateach end of the body 24.

Means are provided for sealing the pistons and piston chambers againstthe loss of hydraulic fluid and for causing the hydraulic fluid totravel in a tortuous path when the device is being bled, said meansincluding a flexible annular sealing ring or gasket lll disposed aboutthe reduced shank portion. til of each piston 22, 23 in sealing relationwith the walls of the piston chambers 26, 2?. An annular expander memberit encircles the shank of each piston, tl is expander having a beveledportion t l adapted to project into the recess in the sealing ring 42 toexpand the sealing ring responsive to the pressure of a coiledcompression spring to which is interposed between the expander t3 andthe central partition the expandel i having an annular shoulder for onegeinen by the spring at.

iiu1o-dircct1 a means for causing the hydraulic pressure fluid to travelin a tortuous path when the device is bled, includes a transverse grooveor recess 6-8 which is transversely disposed across the inner end, ofthe reduced if. of each of the pistons 22, so as to wit tie smallpassage tsrough the l tition 25 of the wheel cylinder. In

formed ember or "7911(161 it, those or a pair or set of annularly spacedv 'tical grooves it in the outer vertical peripheral wall and a secondpair or set of vertically disposed pa sages E in a; iularly spacedrelation through shoulder with which the spring i6 is engaged, thisshoulder il also coopelively about its inner periphc. l surface with theshank 3t oi the pistons for prcpciy "ioning the expander about saidpistons in the piston chambers 26, Ill. The enaflce i is alsoprovidedwith a third pair or set of fiuid-directr .on in an anall fill. off tiand r2 best 5 and and it will be so annnlarly dis pl- "i" l, althought1; with each other lges be i a any d formfthe reduced shank 38' of thepiston 23' is shortened to some extent and the piston chamber 21 isenlarged at its outer end to provide a stop shoulder 53 against which anenlarged head 54 on the outer end of the piston 23 is adapted to abutfor limiting inward movement of the piston 23. In this modified form,moreover, there is no need for the transverse grooves 48 with which thepistons 22, 23 are provided, as will be apparent from the followingdescription of the operationof a wheel cylinder made in accordance withthis invention.

When it is desired to bleed the wheel cylinders "I, 8, the bleeder valve(not shown), which is located in the enlarged portion 33 of the bleedpassage 32 throughthe portion 28 of each wheel cylinder, is opened.Pressure produced by the master cylinder (not shown) will then force thehydraulic fluid through the inlet passage 30 into the piston chamber 21,the fluid being deflected I by the shoulder 41 on the expander 43, whichcauses the fluid to flow around the reduced shank 36 of the piston 23until it finds access to the vertical passages 5! through the shoulder41. The fluid will then fiow between the inner lip of the sealing ringor gasket 42 and the expanding edge of the expander 43 into the recess45 of thesealing ring 42 where it is again deflected and caused to swirland wash out any air bubbles or pockets which may be present, and fromthere through the passages 52 in the inclined portion 44 of the expander43. The fluid is then again deflected and caused to wash around theinclined face 44 of the expander, until it reaches the vertical passages49 through the vertical portion 50 f the expander, and from there, thefluid flows freely through the passages 49 to the inner end of thepiston chamber 21 where it enters into the open ends of the transversegroove 48 in the inner end of the piston 23, thence flowing through thereduced passage 35 into the piston chamber 26 where it is deflectedlaterally through the groove 48 in the piston 22. From here, the fluidflows upwardly through the passages of the expander 43 encircling thepiston 22, thence into the recess 45 in the upper sealing ring 42, andthence downwardly through the passages 52 in the inclined portion 44 ofthe expander ring 43, and finally through the bleed passage 32, asgenerally indicated by the directional arrows in Figures 2 and 3.

Thus it is apparent that the fluid is being continually deflected andre-directed by the expander rings 43 in the piston chambers 26, 21 insuch manner as to cause the fluid to travel in a tortuous path and toswirl and wash small bubbles of air that tend to cling to the surfacesand corners out of the actuator cylinder, this tertucus travel of thefluid being caused by the annularly displaced passages 5!, 52, and 49through which the fluid must flow, as well as by the shoulders 41 andthe flat faces 44 of the expander rings 43 about which the fluid mustflow in order to gain access to the aforementioned passages.

It will be understood from the above that the bleeding procedure asdescribed in the foregoing can be performed separately for each of theactuators 1 and 8, or simultaneously if preferred, and in either case,the pressure fluid should be forced through the hydraulic system andthrough the wheel cylinders until all air has been effectively flushedor washed out of the system. Thereafter, the system can be refilled withhydraulic fluid to replenish any fluid that is lost or 8?. wastedbyth'fl'u'shing operation; and to insure an adequate supply of pressurefluid in the system to enable the brake to be properly operated in theregular manner, under the control of the usual master cylinder.

While the specific details of the'invention have been herein shown anddescribed, the invention is not confined thereto as changes andalterations may be made without departing from the spirit thereof asdefined by the appended claims.

We claim:

1. A fluid pressure responsive actuator device of the class described,comprising a body having a piston chamber therein, and a piston disposedWithin said chamber, said body being provided with a pressure fluidinlet-outlet opening and also with a bleed opening, both of saidopenings communicating with said chamber, and fluiddirecting meanswithin said chamber for directing the pressure fluid in a tortuous paththrough said chamber and around said piston to the bleed openingaforesaid when a pressure fluid is forced through the device, saidfluid-directing means comprising an annular member encircling saidpiston and having fluid passages therein.

2. A fluid pressure responsive actuator device of the class described,comprising a body having a piston chamber therein, and a piston disposedwithin said chamber, said body being provided with a pressure fluidinlet-outlet opening and also with a bleed opening, both of saidopenings communicating with said chamber, and fluiddirecting meanswithin said chamber for directing the pressure fluid in a tortuous paththrough said chamber and around said piston to the bleed openingaforesaid when a pressure fluid is forced through the device, saidfluid-directing means comprising an annular member encircling saidpiston and. having fluid passages therethrough, the fluid passages beingdisposed at diametrically opposite positions about the central axis ofsaid annular member.

3. A fluid pressure responsive actuator device of the class described,comprising a body having piston chamber therein, and a piston disposedwithin said chamber, said body being provided with pressure fluidinlet-outlet opening and also with a bleed opening, both of saidopenings communicating with said chamber, and fluiddirecting meanswithin said chamber for directing the pressure fluid in a tortuous paththrough said chamber and around said piston to the bleed openingaforesaid when a pressure fluid is forced through the device, saidfluid-directing means comprising an annular member encircling saidpiston within said cylinder and having a plurality of fluid-directingpassages therethrough, said passages being disposed at circumferentiallyspaced positions about the annular member.

4. A fluid pressure responsive actuator device of the class described,comprising a body having a piston chamber therein, and a piston disposedwithin said chamber, said body being provided with a pressure fluidinlet-outlet opening and also with a bleed opening, both of saidopenings communicating with said chamber, and fluiddirecting meanswithin said chamber for directing the pressure fluid in a tortuous paththrough said chamber and around said piston to the bleed openingaforesaid when a pressure fluid is forced through the device, saidfluid-directing means comprising an annular member encircling saidpiston and having its inner periphery engaged with said piston and itsouter periphery having .a portion engaged with the wall of the pistonchamber, said annular member having-a plurality of fluid-directingpassages circumferentially spaced about the inner periphery aforesaidand a plurality of fluid-directing, passages circumferentially spacedabout the outer periphery aforesaid.

5. A fluid pressure responsive actuator device of the class described,comprising a body having a piston chamber therein; and a piston disposedwithin said chamber, said body being provided with a pressure fluidinlet-outlet opening and also with a bleed opening, both of saidopenings communicating with said chamber, and fluiddirecting meanswithin said chamber for directing the pressure fluid in a tortuous paththrough said chamber and around said piston to the bleed openingaforesaid when a pressure fluid is forced through the device, saidfluid-directing means comprising an annular member encircling saidpiston and having its inner periphery engaged with said piston and itsouter periphery having a portion engaged with the wall of the pistonchamber, said annular member having a plurality of fluid-directingpassages circumferentially spaced about the inner periphery aforesaidand a plurality of fluid-directing passages circumferentially spacedabout the outer periphery aforesaid, the fluid-directing passages aboutsaid inner periphery being annularly displaced with respect to at leastsome of the fluid-directing passages about said outer periphery.

6. A fluid pressure responsive actuator device of the class described,comprising a body having a piston chamber therein and a reciprocablepiston disposed within said chamber, said body being provided with apressure fluid inlet-outlet opening and also with a bleed opening, saidpiston being engageable with said body for limiting movement of saidpiston in one direction, and an annular member disposed about saidpiston within said piston chamber, said annular member including meansfor directing pressure fluid in a tortuous path through said chamber andaround said piston to the bleed opening aforesaid when a pressure fluidis forced through the device.

7. A fluid pressure responsive actuator device as deflned in claim 6,wherein the piston comprises a shank portion engageable with said bodyfor limiting movement of the piston in one direction as aforesaid.

8. A fluid pressure responsive actuator device as defined in claim 6,wherein the body is provided with an annular shoulder near the outer endof the piston chamber, and the piston is provided with an annularshoulder engageable with the shoulder on said body for limiting movementof the piston in one direction as aforesaid.

9; A hydraulic actuator of the class described,-

comprising a body having opposed inter-communicating piston chamberstherein, and oppositely shiftable pistons disposed within the respectivepiston chambers, said body having a pressure fluid inlet-outlet openingcommunicating with one of said piston chambers and also a bleed openingcommunicating with the other of said piston chambers, and afluid-directing member disposed about each of said pistons within saidpiston chambers for directing a pressure fluid in a tortuous paththrough each of said piston chambers and about said pistons to saidbleed opening when a pressure fluid is admitted into the inlet-outletopening and forced through the actuator.

10. A hydraulic actuator as defined in claim 9, wherein eachfluid-directing member is of annular form and is provided with an innerand an outer cylindrical surface, said outer cylindrical surface beingextended at one end at an angle and inclined towards said innercylindrical surface, said inner cylindricalsurface being pro vided withan annular shoulder extending radial- 1y inwardly therefrom, saidshoulder having a set of axially extended fluid passages therethrough,said outer inclinedsurface having a set of fluid passages also extendedaxially therethrough, and said outer cylindrical surface also having aset of fluid passages axially extended therethrough.

11. A hydraulic actuator as defined in claim 9, wherein thefluid-directing member is of annular form and is provided with an innerand an outer cylindrical surface, said outer cylindrical. surface beingextended at one end at an angle inclined towards said inner cylindricalsurface, said inner cylindrical surface being provided with an annularshoulder extending radially inwardly therefrom, said shoulder having aset of axiall extended fluid passages therethrough, said outer inclinedsurface having a set of fluid passages also extended axiallytherethrough, and said outer cylindrical surface also having a set offluid passages axially extended therethrough, the set of passagesthrough said shoulder and said outer cylindrical surface being annularlydisplaced with respect to the set of passages through said inclinedouter surface.

12. An actuator device for hydraulic brakes and the like, comprising abody having a pair of opposed piston chambers therein, a centralpartition separating said piston chambers and hav ing a restricted fluidpassage therethrough for establishing inter-communication between saidopposed chambers, oppositely reciprocable pistons in the respectivepiston chambers, said body also having an inlet-outlet passage extendinginto one of said piston chambers and having a bleed passage extendinginto the other piston chamber, a flexible annular sealing gasketencircling each of said pistons, and an annular expander member engagedwith each of said sealing gaskets, said expander members each havingmeans for directing a pressure fluid in a tortuous path through itscorresponding piston chamber when a pressure fluid is forced through thedevice from said inlet-outlet passage to said bleed passage.

13. An actuator device as defined in claim 12, wherein the pressurefluid directing means comprises an internal shoulder on the expandermember engageable with said piston and having a set of fluid passagestherethrough, an angularly disposed exterior surface for expandingengagement with said sealing gasket and having a second set of fluidpassages therethrough displaced with respect to said first set, and acylindrical exterior surface engageable with the wall of said pistonchamber and having a third set of fluid passages therethrough displacedwith respect to said second set.

14. An actuator device as defined in claim 12, wherein the inner end ofeach piston is provided with a transverse groove in register with thepassage through said partition for enabling the pressure fluid to flowfrom one piston chamber into the other when the inner end of eitherpiston is in engagement with said partition.

15. A fluid-directing member of the class described, comprising anannular member having an inner periphery and an outer periphery, saidinner periphery being provided with a shoulder having a set of fluidpassages therethrough, and

11 said outer periphery having a relatively straight wall and anangularly disposed wall, each wall having a set of fluid passagestherethrough.

16. A fluid-directing member as defined in claim 15, wherein the set offluid-directing pas- 5 sages in the angularly disposed wall isannuIa-rly displaced with respect to the set of fluid passages throughsaid shoulder, and the set of fluid passages through the relativelystraight wall is annularly displaced with respect to the set of fluid 10passages through said angularly disposed wall.

CLAUDE R. MYERS. LESTER F. DASSE. JOHN BASSETT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Dick July 13, 1939 Bowen Sept. 17, 1940 Bock Sept. 17, 1940Fike June 27, 1950 Christensen Oct. 16, 1951

